Flexible conductor for induction heating



Jan, 4, 1949.

H. A. STRICKLAND, JR

FLEXIBLE CONDUCTOR FOR INDUCTION HEATING Filed Sept. 2, 1944 INVENTORI B Pi /1% ATTORNEY Patented Jan. 4, 1949 FLEXIBLE CONDUCTOR FOR INDUCTION HEATING Harold A. Strickland, In, Detroit, Mich assignor,

by mesne assignments, to The Ohio Crankshaft Company, Cleveland, Ohio, a corporation of Ohio Application September 2, 1944, semi No. 552,102

4 Claims. 1

This invention relates to inductive heating equipment and has particular application to the heating of furnace chambers which are of irregular formation preventing the usual application of a heating coil thereto, or to pieces too large to be conveniently loaded'into heating coils, or to pieces where there is not enough production to warrant building of a special coil.

In certain furnaces adapted for inductive heating the irregularity of shape frequently makes it difficult to apply a prepared wound coil closely to the furnace exterior so as to obtain maximum heating efficiency. For example, in the case of a tubular furnace having enlarged ends it is impossible to insert a wound coil over the ends and at the same time have the coil lie closely against the tube exterior after placement.

Accordingly, it is one of the primary objects of the present invention to provide a conductor of such construction as will permit application of the same directly to a furnace, without prior winding in coil formation. Another object is to provide a tubular conductor for inductive heating which may be bent about a curved form without material flattening of the tube. Another object is to provide a flexible water-cooled conductor with high current carrying capacity and with good electrical and thermal insulation. Another object of the invention is to provide a conductcr which is susceptible to bending without strain upon the electrically insulating covering of the conductor. Still another object is to provide a conductor for inductive heating which is provided with external insulation having a fixed external diameter. Other objects of the invention will appear on consideration of the embodiment of the invention hereinafter described and shown in the accompanying drawing in which:

Figure 1 is a view showing an inductive heating unit or furnace with my conductor applied thereto;

Figure 2 is a longitudinal section through the conductor; and

Figure 3 is a sectional view of a modification of the conductor.

Referring to Figure 1, I have indicated the coil support generally by the numeral i the same comprising a tube or chamber 2 provided with enlarged terminal members 3 and l; and a flexible conductor generally indicated by the numeral 5 wound about said chamber. The conductor 5 is in the form of 'a-tube 6 having a corrugated wall 1 except for the ends 8 which may be cylindrical in shape as shown in Figure 2. This tube is preferably made of copper or other metal highly con- 2 *ductlve with reference to electricity. Adapted to be secured over the cylindrical ends 8 of the conductor are terminal connectors 9 which may take any desired form. Figure 2 illustrates a connector having a conductor engaging section i0 and a pipecoupling section ii of reduced diameter adapted to couple with a pipe line from which a coolant may be derived for passage through the tube for preventing the temperature of the conductor from becoming excessive. Section 10 is preferably formed with a lug l2 having an aperture i8 adapted for engagement with a supply circuit I3 of electrical current; As indicated this circuit includes a transformer I4 and a capacitor IS in parallel therewith to increase the power factor of the circuit.

The tube 1 of the conductor is provided with a plurality of insulating and refractory rings i6 which may be of any suitable material such as a ceramic substance. These rings I6 preferably also are rounded at the adjacent edges thereof as indicated by the numeral i1 and in mounting the same the rings are slightly displaced'longitudinally with reference to the tube so that when the conductor is bent about the curved exterior of the support I, the rings readily yield to permit adjustment to the new position with maintenance of insulation on the chamber.

It is pointed out that while the rings as above described may be yieldable in substance prefer ably they are rigid and hence the external diameter of the rings is constant. In effect this secures for the conductor as a whole a constant diameter and insures maintenance of a predetermined density of winding per unit length as required for the desired heating function of the device. This uniform diameter of the rings is paralleled by the tube in that since the wall of the tube is corrugated, on bending the change of arc as between the radially inner and outer surfaces of the section of the conductor is absorbed by the yield of the corrugations so that within reasonable limits of use an approximate circular section of the tube is maintained during the bending operation. This may be contrasted to tubing the wall of which is cylindrical or of uniform size along its length which therefore on bending flattens thus increasing the width of the successive turns of the coil and consequently, in the case of rigid rings, causing binding therewith, and in the case of flexible rings, reducing the number of effective turns for each unit length of the 0011.. Consequently, it appears that there is a particular combination between the employment of a tube having a corrugated wall and its use in inductive heating, since by employment of corrugations, the efficiency oi! the conductor is preserved after bending.

While the metal tube 1, as shown in Figure 2, is under ordinary circumstances ample for the q t ty or current used by the device, under some conditions it may be desirable to increase the cross sectional area of the conductor. This may be accomplished by the auxiliary conducting element 20 shown in Figure 3 comprising a flexible metallic element axially positioned with reierence to the tube 2| and having its ends extending through a wall 22 in a modified Iorm oi terminal connector 23 where it is fastened by welding, brazing to other appropriate mean as indicated by the numerals 24 and 25, As illustrated, the connector 23 is preferably provided with a lateral coupling connection 28 so that the end plate 22 may be appropriately in line with the axis oi the tube 2i for adjustment of the aux iliary conductor element 20. The connector 23 is also provided with a circuit connection lug 21. The insulating rings 28 are similar to those of the first modification but in the conductor tube instead of annular corrugations lying in right angled planes to the tube axis as shown in Figure 2, the corrugations are spiral.

Variations of structure other than those described may be made and hence no limitations are intended by the described forms other than may be required by the claims hereto appended.

What is claimed is:

1. An induction heating cable adapted to be coiled about an article to be heated comprising, a conductor including a corrugated metal tube, conduction connectors at the ends of said tube, and a plurality of rigid insulating rings loosely spaced along said tube a distance less than the axial length of said rings intermediate said connectors in close proximity to said tube, said rings adapted to control flexures of said tube throughout its length whereby to prevent radial collapse thereof.

2. An induction heating conductor comprising a corrugated metal tube, conduction connectors at the ends of said tube, and a plurality of rigid insulating rings loosely spaced along said tube intermediate said connectors in close proximity to said tube, the edges of said rings being curved whereby bending of the tube with the attached rings into a coil is facilitated.

3. An induction heating cable comprising, a tubular corrugated conductor, a plurality of rigid, insulating rings loosely mounted on and in close proximity to said conductor, terminal connectors secured to said conductor to confine said rings loosely thereon, and an auxiliary conductor fastened to said connectors and positioned within said tubular conductor, said rings facilitating bending of the tube with the attached rings into a coil.

4. A cable for induction heating adapted to be coiled into an inductor comprising a flexible metal tube having a tendency to flatten beyond excessive bending, conduction connectors at the ends of said tube, and a plurality of axially short adjacent, rigid, insulating rings loosely spaced along said tube intermediate said connectors in close proximity to said tube, said rings being spaced a distance less than their axial length, the opposed faces thereof adapted to abut along the inner edge when .the cable is coiled, said rings being adapted to prevent localized fiexure of said tube when being coiled into an inductor,

HAROLD A. STRICKLAND, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,179,577 Sundh Apr. 18, 1916 1,257,669 Bliss Feb. 26, 1918 1,505,121 Aliport Aug. 19, 1924 1,640,744 Zapf Aug. 30, 1927 1,723,984 Von Henke Aug. 6, 1929 1,878,790 Lund Sept. 20, 1932 1,911,470 Rosner May 30, 1933 OTHER REFERENCES Publication Iron and Steel Engineer, for March 1933, page 79; Figs. 14A and 14B. 

